The present invention relates generally to suspension systems for wheeled vehicles and, in an embodiment described herein, more particularly provides a steerable lift axle suspension system.
Those skilled in the art of vehicle suspension system design and manufacture know that it is becoming increasingly important to provide suspension systems which have reduced weight, and which are more compact. These objectives are sought for all types of suspension systems, including steerable lift axle suspension systems. However, these objectives are particularly difficult to achieve in steerable suspension systems, due to the fact that so many functions are performed by these suspension systems.
For example, a typical liftable steerable suspension system must perform the functions of lifting an axle assembly relative to a vehicle frame, allowing the tires to steer, carrying loads and providing an acceptable ride quality. These last functions are many times satisfied by using a parallelogram-type arrangement of trailing arms pivotably connected between a hanger bracket and the axle assembly. It will be readily appreciated that, with all of the equipment needed to perform all of these functions, decreasing weight and increasing compactness are difficult goals to accomplish.
Therefore, it can be seen that it would be quite desirable to provide a steerable lift axle suspension system which solves the above problems in the art. The concepts used to solve these problems could also be applied to other types of suspension systems, including other liftable suspension systems.